Asbestos yarn



Aug'. 3, 1937. B. H. FOSTER 2,089,021

ASBESTOS YARN Filed Sept. 22, 1936 2 Shets-Sheet 1 lNVENTOR ATTORNEY1937- B. H. FQISTYER 2,089,021

ASBESTOS YARN Filed Sept. 22, 1936 2 Sheets-Sheet 2 Patented Aug. 3,1937 ASBESTOS YARN Boutwell 1!. Foster, Maplewood, N. 1., assignor toUnited States Rubber Products, Inc., New York, N. Y., a corporation ofDelaware Application September 22, 1936, Serial No. 101,922

18 Claim.

This invention relates to new and improved asbestos yarns, and moreparticularly to a drafted asbestos yarn.

The present application is a continuation-inpart of my copendingapplication Serial No. 2,221, filed January 17, 1935.

Asbestos yarn is widely used in the arts in the making of fabrics forfire curtains and other fire proofing purposes, clutch facings, tapes,brake lining, and many other applications. In the method previously usedfor making commercial yarn, the relatively short asbestos fiber afterpassing through the usual preparatory operations, such as crushing,opening and cleaning, is mixed or blended with a small proportion of avegetable fiber, usually cotton, and then carded. The percentage ofcotton may be varied to some extent, but it is usually employed in theamount of about 15%. With a less cotton content than this, with therelatively short asbestos fiber stock in use, considerable difllcultyhas been had in the carding and spinning operations. However, recentimprovements in carding and otheroperations have enabled spinnablerovings to be made containing as low as 8% cotton. In passing throughthe carding operation, the carded web is split into narrow strips whichare thereafter compacted by rolling them between rub aprons to formrovings. The rovings are then passed through a pair of delivery rollersto a mule or ring spinning frame and spun without drafting. Accordingly,it has been necessary to prepare a different size of roving for theproduction of each different size of yarn. Hence it is seen that theso-called spinning of prior commercial asbestos yarn is in realitymerely a twisting operation.

Drafting systems as employed in the production of yarns from fibrousmaterials other than asbestos have not been applicable to the draftingof asbestos'rovings, due to the weakness, short fiber length, lack ofcohesion, and other characteristics of the asbestos fiber used. Asbestosyarns as prepared by prior commercial methods, are unbalanced, uneven,rough, loosely compacted, relatively coarse and can be made only at arelatively low speed. Furthermore, the finest gauge of such asbestosyarn which it is feasible to manufacture on a commercial scale by theprior methods is about 35-cut, the same having a maximum twist of about17 turns per inch, and

such fine yarn could only be made by the use of the #1 grade fibre, or amixture of this and #2.

An object of the present invention is to provide a drafted and twistedasbestos yarn.

Another object is to provide asbestos ya n of more uniform size andquality, greater strength and compactness, better balance, and, for agiven size, a cheaper yarn.

Another object is to provide asbestos yarn of 10 finer gauge and abalanced yarn with higher twist than has heretofore been obtainable.

1 Another object is to provide asbestos yarns in the finer sizes whileemploying fibres of such short staple that they could not previously beused for this purpose.

For a detailed disclosure of the nature and objects of the invention,reference is had to the accompanying specification and drawings, inwhich latter: I

Fig. 1 is a diagrammatic side elevation of a suitable form of apparatusfor making the improved yarn;

Fig. 21s a diagrammatic plan view of the drive mechanism for the variousparts; 25 Fig. 3 is a detail on a larger scale of a modified form ofdrafting apparatus; Fig. 4 is a similar detail of another modified formof drafting apparatus;

Fig. 5 is a similar detail of still another modification and Fig. 6 is asimilar detail of a still further modification.

In making the yarn, an asbestos roving, which may be formed by the usualmethods, may be led first through a wetting bath, then through asuitable draftlng mechanism, and thence to a suit- Y able twistingdevice, such as an ordinary ring monly used forms of wetting agents aresalts. such as the sodium salts, of sulphonated hydrocarbons,sulphonated higher alcohols and esters or suiphonated fatty oils, amongwhich are the trade products "Alkanol" and Gardinol, which are,

respectively, a salt of a sulphonated naphthalene and a salt of asulphonated higher alcohol, such as lauryl or oleyl alcohol. As anexample, in the present invention Gardinol may be used in aconcentration of about 0.5%, or "Alkanol" in a concentration of about0.2%.

It has also been found advantageous to add to the wetting bath, inaddition to the wetting agent, a small proportion, such as 1%, of rubberlatex unvulcanized or vulcanized, this amount of latex improving thespinning qualities of the roving but being indiscernible in the finishedyarn. It is believed the latex acts to increase the resistance todrafting and/or make such resistance more uniform. ,Materiais havingequivalent properties may be used instead. However, excellent resultsmay be obtained by wet drafting with water alone, or with watercontaining a small amount of glycerine.

Preferably the drafting operation is carried out in such manner that anydistance over which the asbestos roving is mechanically unsupportedduring its passage through the drafting mechanism is not substantiallygreater than the effective mean length of the fibers composing theroving, whereby the drafting is effected smoothly and without theformation of undue thick and thin places.

The drafting mechanism may comprise two or more successive pairs ofrolls rotating at progressively greater speeds, as'in the drafting ofother types of fibers, a suitable draft being from 2:1 to as high as 6:1or 8:1.

The present invention, while equally applicable to a yarn drafted fromthe #1 or #2 grade of asbestos fibres, relates particularly to a draftedand twisted asbestos yarn made from relatively short staple asbestosfibers, such as have been previously used in making undrafted andtwisted asbestos yarns in the range of sizes from 10-20 cut. Generally,the effective or virtual staple length of such asbestos fiber has beenfound to be approximately 0.5 men. A special advantage of the presentinvention is its application for spinning such short fibers as are knowncommercially as the No. 3 or spinning quality grade and are divided intovarious classes by means of a standard and well known test which is asfollows: Four superposed boxes are provided, the top one of which has ascreen bottom with $6" openings, the wire of the screen being of adiameter of .105". Below this box is a second box provided with a screenbottom of four meshes to the inch, the wire of the screen being of adiameter of .063". Below this box is a third one having a screen bottomof ten meshes to the inch, the wire of which is of .047" diameter. Belowthis is a fourth box with an imperforate bottom. In testing a sample ofasbestos fiber, one pound of the fiber is placed in the top box'an'd theboxes are rapidly reciproc'ated for a period of two minutes, and theamounts of fiber remaining in each of the boxes are then weighed. Thefourth box will contain the dust and fines.

- quality grade of asbestos fiber is classified as follows:

Oz. perlb.

Glass Box 1 Box 2 Box 3 Box 4 While any of the above classes of thespinning quality fiber, or their equivalent, may be utilized in thepresent invention, or mixtures of them, the preferred classes are Nos. 3to 6. Classes 1 and 2 are more expensive and the supply too limited tobe relied on for the commercial production, and classes! and 8 containsuch a large proportion of very short fiber asbestos that they arediilicult to card and make into yarn without the addition of anundesired amount of cotton fiber. In the present invention, it ispreferred not to use more than 25% cotton, and this may be decreased toas little as 8% or 10%, the higher the percentage of longer flberedasbestos, the less amount of cotton required.

While special constructions may be provided for drafting and properlysupporting the asbestos roving, as will be later disclosed, it ispreferred for commercial convenience to utilize to a partial extent atleast present machinery such as that provided for the drafting of cottonrovings, and modify the same to-provide the desired additional supportfor the roving between successive pairs of rolls, the latter being leftwith the same spacing as for drafting cotton.

In Fig. 1, there is shown a diagrammatic side view of one form of cottonspinning mechanism as modified for carrying out the process of thepresent invention. In this figure the numeral i designates a package'ofasbestos roving which is supported at one end by a suitable spindle topermit drawing off the roving with a minimum of tension. The roving 2 isled from the package over a guide I and under a guide 4, the latterbeing disposed below the surface of a wetting .bath in the receptacle 5.After passing through the wetting bath, the roving is led over a guideroll 0 and then passes through the drafting mechanism. This mechanism inthe .form shown consists of a lower back roll 1, an upper back roll I, alower front roll 9, and an upper front roll I, with a small intermediateroll ii disposed to press lightly against the upper back roll I and befrictionally driven thereby. The lower rolls I and 9 are theconventional fluted steel rolls, the upper rolls 8 and iii are rubbercovered, and the small roll II is a metal roll provided with small,closely spaced circumferential grooves. The lower rolls 1 and0- arepositively driven while the upper rolls 8 and i0 are idler rolls whichare pressed against the lower rolls.

By the construction shown and described, the asbestos fibers of theroving, which roving may or may not be lightly twisted, after passingthe nip of the back rolls 1 and l, are gripped firmly enough at the nipbetween the small roll ii and the upper back roll 8 to enable them to bedrafted by the pull of the front rolls I and IO.

4 while the. cotton fibers are effectively ripped by the back rolls 1and 9 and, because of their greater strength, are able to slip throughthe nip provided by the rolls ii and 9. Thus the asbestos and the cottoncomponents of the roving, respectively, are drafted concurrently fromtwo different nips, each of which is located at the most advantageousdistance from the'front rolls for the proper drafting of the respectivecomponent upon which it is to operate, the distance over which theasbestos fibers are drafted being roughly one-half of that for thecotton fibers. The adherence of the wet roving to the auxiliary roll IIalso serves to prevent the asbestos fibers from being dragged ahead bythe cotton fibers, thus aiding to prevent the formation of undue thickand thin places.

If additional main drafting rolls are employed,

' the small auxiliary roll. Il may also be duplicated.

After it issues from the rolls 9 and I9, the drafted roving passesthrough a pigtail guide l2, through the traveller i 3 on ring l4, and iswound up as a twisted .yam on a bobbin I5 on the spindle l8.

In Fig. 2 there is shown one form of drive mechanism for the apparatus,said mechanism consisting of a motor i! which through the belt l8 drivesa pulley l9 on one end of a cylinder 29. Passing over this cylinder 29are a series of .drive belts 2| for the whirls 22 of the spindles I6. Atthe opposite end of the cylinder 20 there is mounted a gear 23 whichthrough the intermeshing gears 24, 25 and 26 drives a gear 21 carried bythe front draft roll 9 at one end. At the opposite end of the frontdraft roll is carried a gear 28, which through the intermeshing gears29, 30, 3i and 32 drives a gear 33 carried at the end of the rear draftroll I.

The gear 25 is interchangeable, and by varying the number of its teeththe speed of roll 9 can be varied, thus regulating the amount of twistbeing put into the yarn. The gear 30 is also interchangeable, and byvarying the number of teeth on this gear, the speed of the rear draftroll I may be varied to thus vary the draft, or the ratio of surfacespeed of the front roll 9 to that of the rear roll i.

In Fig. 3 there is shown on an enlarged scale a modified form ofdrafting mechanism comprising a lower back roll 94, an upper back roll35, a lower front roll 36, and an upper front roll 31. Extending aroundthe lower rolls 34 and 96 is an'extensible rubber apron 39, and a smallidler roll 39 may be disposed to cooperate with the apron at a pointbetween the front and back rolls. This small roll 39 may be entirely ofmetal such as steel. In this form the lower rolls 94 and 36 arepositively driven, while the upper rolls 35 and 31 are idler rolls andare covered with rubber in the conventional manner.

In the operation of this form of drafting mechanism the roving is fedbetween the upper back roll 35 and the apron 38, and is then carried bythe apron to the nip between the upper front roll 91 and the apron, theroving being thus supported over the entire distance between the hips ofthe back and the front rolls. The pressure of the upper rolls againstthe apron and the lower rolls is sufficient to prevent the apron fromslipping, whereby the pull exerted by the front rolls stretches theupper course of the apron in proportion to the ratio between the surfacespeeds of the front and back rolls, the

apron retracting upon leaving the lower front roll. Thus the roving andthe apron are drawn out to the same extent as they issue from the nip ofthe back rolls and-there is substantially no relative motion between theupper course of the apron and the roving as the latter lies upon theapron.

The control of the fibers in this modification may be further increasedif desired by the provision of the auxiliary small roll 39 which isdisposed in contact with the upper face of the extensible apron at apoint intermediate of the back and front rolls.

In Fig. 4 there is shown a further modification of the conventionalcotton drafting mechanism. In this modification there are provided alower back roll 49, an upper back' roll 4|, a lower front roll 42 and anupper front roll 43, An inextensible apron 44 of any suitable material,such as rubberized fabric, extends around the lower front roll 42 andaround a small auxiiiary roll 46, so that the apron 44 provides asupport for the roving over a substantial portion of its path betweenthe front and back rolls. A second inextensible apron 49 passes over theupper front'roll 43 and also over a second small auxiliary roll 41situated immediately above the first auxiliary roll 45. However, ifdesired, the second apron 46 may be omitted and the nip at the front ofthe drafting mechanism be provided directly between the'top front roll43 and the apron 44. In this form the lower rolls 49 and 42 arepositively driven while the upper rolls 4! and 43 are idlers. The roll4| may be rubber covered in the conventional manner.

The drafts possible with asbestos rovings are relatively low as comparedwith other textile fiber materials, and hence the invention has beenillustrated with the use of only two pairs of rolls in the draftingframe, since this number is adequate, but if desired, intermediate rollsmay be used.

In Fig. 5 there is shown a form of drafting mechanism which essentiallyconsists of a number of pairs of relatively small bottom and top rolls.In the drawings there have been illustrated four pairs of rolls but thisnumber may be varied, if desired. In this form the rolls are preferablyof a diameter approximately only one-fourth that of the smallest rollsnow in use in spinning cotton, and spaced quite close togethen Forexample, the rolls may be about to 1'; of an inch in diameter. In Fig. 5there are shown pairs of lower and upper rolls 48 and 49, 59 and Si, 52and 59, and. 54 and 9!. The lower rolls are positively driven atprogressively greater speeds from back to front, while the upper rollsare idler rolls pressing against the lower rolls. All of the rolls arepreferably fluted. It will be seen that in this form of the inventionthe roving is progressively drafted from the back pair to the front pairof rolls and at the same time the roving is never unsupported for adistance greater than the approximate effective length of the asbestosfibers.

In Fig. 6 there is shown another suitable form of drafting mechanismwhich is similar in some respects to that shown in Fig. l of patent toCasablancas #1213344. In Fig. 6 the numeral 56 represents a bottomdriven back roll and an idler top back roll 51. The numeral 58designates the driven bottom front roll. and 59 an idler top front roll.Between the back and front rolls there is disposed a driven bottom rollill around which is disposed an endless rubber apron 9i which alsopasses around a fixed bar 02 of somewhat flattened contour. Acooperating upper apron mechanism comprises a roll 63, an endless rubberapron 64 and a flattened fixed bar I.

In spinning frames of the type shown in Fig; 1 of the Casablancaspatent, the aprons or belts are made of thin leather, and they approacheach other just closely enough to barely contact with the roving so asto support and feed it forward. Also the bars around which the apronspass at the front are rounded, so that at the forward end of the nipbetween the two aprons the aprons diverge rather suddenly and widely.Also the belts or aprons are so spaced from the front rolls that the endof their nip is more than of an inch from the nip of the front rolls.

In the construction employed in Fig. 6 of the present invention, thebelts or aprons 0| and N are relatively thick and made of rubber andtheir spacing is such that the belts will firmly but resiliently gripthe roving passing through them so as to frictionaliy hold it and causethe drafting of the asbestos fibers between the nip of the belts and thenip of the front rolls. The flattened bars 62 and 65 enable the nip ofthe belts to approach closer to the nip of the front rolls, and thebelts do not diverge from each other so suddenly at the front end oftheir nip. By reason of this construction the unsupported distance overwhich nip to the nip of the front rolls is of the order of 55th of aninch and preferably a half inch or less. By reason of the describedconstruction, the unsupported distance through which the roving passesduring its drafting is very short, and as a result the apparatus willsuccessfully draft relatively short asbestos fibers.

In the asbestos art rovings and yarns are described in terms of thenumber of yards per pound, and the word "cut is used to designate a'unit of 100 yards. Therefore, this word, preceded by a number, indicatesin multiples of 100 yards, the yardage per pound of a roving or a yarn.For example, a IO-,cut yarn" indicates that a pound of the yarn measuresapproximately 1000 yards; 18-cut indicates a yarn that measuresapproximately 1800 yards per pound. A very the roving passes from thefront end of the belt given:

TABLI I No. 1 Canadian crude B A AXB P t Rovingelon- Twist gg pm: Yanz-01 0111 1111. R 1 ti 810 511 833g; i peg ll S H! 0 Q 8 VB 8 DC (mmlml)size strand strength break 10 None 0 2.2 0.3 .041 0 is None 111 1.4 4.0.040 0 20 None 20 1.1 40 5.0 .021 12 35 None 31 1. 2 44 4.3 .015 11 10 2is 2.0 41 1.5 .020 13 10 2 22 3.3 13 0.3 .023 12 10 3.1 20 2.4 02 4.4.010 14 10 5.3 55 1.5 03 4.2 .013 20 15 3.1 44 1.3 43 3.3 .010 21 15 5.310 0.00 50 1.0 .010 24 15 53 00 0 51 34 1.0 .011 45 11 2.1 31 1.3 40 2.1.011 1a 11 3. 1 51 o. 00 40 2.1 014 10 10 3.1 02 1.1 00 20 .011 22 105.3 110 0.44 4s 1.0 .000 32 10 as 120 0.40 40 1.3 .001 21 10 03 135 0.20as 1.1 .001 32 10 5.3 40 1.5 00 0.1 .014 20 (2 ends) 3.1 31 2.2 03 4.4.010 12 (2 ends) i No. 1 Canadian crude is a commercial asbestos fiberaveraging staple length.

Tsar: II

No. 3 grade spinning quality fiber (Class 5) In the above tables theyarn of Example was made with a concentration of 0.5% "Gardinol" inwater as a wetting agent, the yarn of Example was made with the use of0.5% "Alkano and the yarns of Examples 6 to 9 and 11 to 24 inclusivewere made with the use of 0.2% "AlkanoP. Also in Examples 8, 15 to 19and 23 there was included 1% of a 25% concentration latex in the wettingbath. In the above tables Examples 1 to 4 and are blanks and are givento show the characteristics of undrafted and unwetted asbestos yarnsmade by prior art methods. Obviously in an asbestos yarn made from anundrafted roving the size-cut should be the same for the finished yarnas for the roving, and it will be noted in the above tables that this isnot strictly correct for Examples 1, 4, and 20. The discrepancy iscaused by the fact that the noiiiinal cut-sizes of the rovings used inthese examples are the sizes as designated by the manufacturer of theroving, while the cut-sizes of the yarns produced were determined byactual weighing of measured lengths ofyarn. The actual size of a rovingmay vary from the nominal size employed without seriously affecting thebalance or kink condition, and that the finished yarn is denser andforthe same cut size is smaller in gauge than the undrafted yarns of theprior art. For instance, in Example 5 the twist per inch was 13 and thecut sizeof the yarn was 18, which gives a twist multiplier of 3; inExample 9 the twist per inch was 21 and the cut size of the yarn was 44.which gives a twist multiplier of 8.2; in Example 11 the twist per inchwas 45 and the cut size of the yarn was 80, which gives a twistmultiplier of 5.5: in Example 12 the twist per inch was 18 andthe cutsize 87, which gives a twist multiplier of 3; inExample 15 the twist perinch was 32 and the cut sire 110, which gives a twist multiplier of 3;and in Example 18 the twist per inch was 20 and the cut size 46, whichgives a twist multiplier of 3.

In order to furnish a still plainer basis for comparison of theadvantages of the present invention over the prior art a series of yarnswere made from the same batch of 10-cut roving of No. 1 Canadianasbestos fiber, the analysis of which yarns is' shown in the followingtable:

TAIL! III a A xxx 35 Twist Em Ont Gauge Draft Yarn-- B gation per pk an(inch) MM E32. .a.

(actual) Obs.)

a 10 ar an 2.4 02 4.2 .022 12 B..... 10 2.1 24 1.4 a4 an .021 12 o 10None 10 as as as .022 5 n'..... 10 None 8 2. l 11 a l .000 a a 1o 21 8a1 as so .000 u fiends r 10 2.1 o u 41 2.2 .osi e I Sends In Examples 13and D no wetting was used.

by as much as 10% or more in either direction.

The figures given in the column headed "Relative strength give thestrength in terms of a hypothetical l-cut' yarn, and accordingly afiorda comparison of the strength of yarns .of diflerent sizes on an equalweight-per-unit-length basis.

In the textile art the twist to be imparted to a yarn is ascertained bymultiplying the square root of the yarn size by a predetermined numbertermed the "twist multiplier, or stated in another way, the twistmultiplier is equal to the number of twists per inch divided by thesquare root of the yarn size.

As previously stated, the finest asbestos yarns which it has beenpracticable to manufacture on a commercial scale by prior methods usingno drafting is about 35-cut, with a maximum twist of about 1'1 turns perinch. In prior art Example 4 of Table I, it will be noted that a rovingof a nominal cut size of 35 had an actual cut size in the finishedundrafted yarn of 37, and the twist per inch was 17, giving in this casea twist multiplier of 2.8. Due to the relative stiffness of the asbestosfibers in commercial asbestos rovings, most of the asbestos yarnproduced heretofore has been made with a twist multiplier of 2 or less,in order to obtain a yarn'more or less balanced which does not kink, andit has been impractical in any case to use a twist multiplier higherthan about 2%. However, it will be noted that by the present inventionthe wetting out of the fibers makes them softer and more-pliable where--by a substantially higher twist multiplier can be In Examples A, C, Eand F the fibers were wet by using a 0.2% concentration of "Aikanol" inwater plus 1% of a 25% concentration latex.

Comparing Examples D, C, B and A, it will be seen that in prior artExample D, using neither drafting nor wetting, the relative strength orstrength factor was 1'1. in C using wetting but no draft the relativestrength was 23, in B using draft but no wetting the relative strengthwas 34, while in A using both draft and wetting the relative strengthwas E2.

In Examples 13 and AthH'e is clear evidenc'of the advantage of usingwetting for the drafting. In both examples the draft and twist wereidentical, and the yarn cut-sizes were very close, considering that thesame uniformity cannot be obtained with asbestos fibers as with ordinarytextile fibers such as cotton. However. it will be noted that therelative strength of the drydrafted yarn-B was 34, while that ofwet-drafted yarn A was 62. It will also be noted that the gauge of yarnB was .027, while that of yarn A was .022, indicating that in the wettedyarn the fibers had been drawn more in parallel and were bettercompacted.

In Examples D, E and 1' the purpose was to compare an undrafted priorart yarn with drafted yarnausing the same twist and as nearly aspossible the same cut-size of finished yarn. It will be noted that inprior art undrafted and unwetted Example D the relative strength was 17,while for drafted and wetted Examples E and 1" it was and 41,respectively. These same examples further indicate the value of thedrafting and wetting in increasing compactness, since in the undraftedExample D the gauge was .056, while in drafted and wetted Examples\E andF the gauges were .030 and .031, respectively.

A desirable feature of the invention is the drafting-and twisting of twoor morerovings to form a single yarn as illustrated in Examples 18 and19 of Table I, Example 24 of Table II, and Examples E and F of TableIII. By drafting two or more rovings and increasing the amount of drafta multiple roving yarn can be obtained of the same size-cut as thatobtained from a single roving with a less amount of draft, and at thesame time the. roving is much more uniform and the breaks or ends downare decreased. For instance, two/rovings of 20-cut size may-be given a'draft of four to produce a finished yarn of approximately 40-cut size,instead of employing a single roving of 20-cut size and giving it adraft of two to produce a finished yarn of approximately 40-cut size.The yarn made from the multiple roving with increased draft will, asbefore stated, be more uniform, and the number of ends down beconsiderably reduced.

It will be seen that by the invention the manufacture of asbestos yarnsof various sizes is greatly simplified, and also cheapened, inasmuch asa wide range of sizes of yarn may be produced from a single size ofroving, merely by varying the speeds of the draft rolls. For example,from a 10-cut roving there may be made any smaller size of yarn down atleast to 55-cut, the latter being materially finer than any heretoforeproduced. Similarly, by the use of a smaller roving, such as 19-cut,there may be made asbestos yarns of extremely fine gauge, such as 60-cutto 135-cut, which yarns are comparable in size with ordinary sewingthreads and greatly extend the field of use of asbestos yarns. The yarnsproduced by the invention are well balanced and may be given a muchhigher twist, especially in finer sizes.

It has also been found that higher spindle speeds may be used withoutincreasing the frequency of breakage, and that a greater yardage of yarnof a given cut-size may be wound on a single bobbin.

The yarns made by the present process are also smaller and more compactthan yarns of the same cut-size made by present commercial methods, andare at least 50% stronger, for yarns of the same cut-size. Furthermore,by the invention low quality asbestos fiber, previously usedonly for theproduction of coarse yarns, may be made into fine yarns of relativelygreater strength. Yarns of greater uniformity may be made according tothe invention by drafting and twisting together a plurality of asbestosrovings to form a single yarn.

Since in the asbestos art theterm asbestos is applied not only toproducts containing asbestos solely but also to products containing aminor amount of vegetable or other fiber, in the claims it is intendedthat the expressions asbestos roving" and asbestos yarn", unlessspecifically limited, shall include asbestos rovings and yarns in whichsmall amounts of other fibers may be included.

While specific embodiments on the invention have been shown anddescribed, it is obvious that modifications may be made therein withoutdeparting from the spirit thereof, and it is not desired to limit theinvention otherwise than as set forth in the appended'claims.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A yarn comprising at least 7. of draf ed and twisted asbestos fibers,the average staple length of said fibers not exceeding three quarters ofan inch.

2. 'A yarn comprising at least 75% of, drafted and twisted asbestosfibers and a minor amount of cotton fibers, the average staple length ofsaid asbestos fibers not exceeding three quarters of an inch.

3. A yarn comprising at least 75% of wetdrafted and twisted asbestosfibers, the average staple length of said asbestos fibers not exceedingthree-quarters of an inch.

4. A yarn comprising wet-drafted and twisted asbestos and organicfibers, the asbestos being at least 75% of the whole, and the averagestaple length of said asbestos fibers not exceeding threequarters of aninch.

5. A yarn comprising at least 75% of wetdrafted and twisted asbestosfibers, said yarn having at least 50% greater breaking strength thanthat of an undrafted twisted asbestos yarn of like size-cut, quality andconstruction, and the average staple length of said asbestos fibers notexceeding three-quarters of an inch.

6. A yarn including at least 75% of wet-drafted and twisted asbestosfibers and a small amount of cotton fibers, the average staple length ofsaid asbestos fibers not exceeding three-quarters of an inch.

7. A drafted and twisted yarn comprising at least 75% of drafted andtwisted asbestos fibers, said asbestos fibers being of a length suchthat up to approximately eight ounces per pound thereof will be retainedon a screen of one-half inch opening, and ten to six ounces on a screenof four meshes to the inch.

8. A drafted and twisted yarn comprising at least 75% of drafted andtwisted asbestos fibers, said asbestos fibers being of a length suchthat approximately from one to four ounces per pound thereof will beretained on a screen of one-half inch opening, and nine to seven ounceson a screen of four meshes to the inch. I

9. Adrafted and twisted yarn comprising at least 75% of drafted andtwisted asbestos fibers, said asbestos fibers being of a length suchthat approximately from eight to fourteen ounces per pound thereof willbe retained on a screen of four meshes to the inch.

10. A drafted and twisted yarn comprising at least 75% of drafted andtwisted asbestos fibers, said asbestos fibers being of varying shortlengths such that approximately from ten to eleven ounces per poundthereof will be retained on a screen of four meshes to the inch.

11. A drafted and twisted yarn comprising at least 75% of drafted andtwisted asbestos fibers, said asbestos fibers being of a length suchthat approximately up to eight ounces per pound thereof will be retainedon a screen of one-half inch opening, ten to six ounces on a screen offour meshes to the inch, and six to one ounces on a. screen of tenmeshes to the inch.

12. A yarn comprising drafted and twisted asbestos and organic fibers,the asbestos being at least 75% of the whole, said asbestos fibers beingcomparatively short and in major part capable of passing a screen ofone-half inch opening.

13. A drafted asbestos yarn having a length of over 3,000 yards perpound, comprising at least 75% of asbestos fibers, the drafted asbestosfibers being comparatively short and in major part capable of passing ascreen of one-half inch opening.

14. A drafted asbestos yam having a length of over 5,000 yards perpound, comprising at least 75% of drafted asbestos fibers and a smallamount of cotton fibers, the asbestos fibers being comparatively shortand in major part capable of passing a screen of one-half inch opening.

15. A drafted asbestos yarn having a length of over 7,500 yards perpound, the drafted asbestos fibers thereof being comparatively short andof a length such that at least fourteen to fifteen and one-half ouncesper pound will be retained on successive screens of one-half inchopening, four meshes to the inch and ten meshes to the inch.

16. A drafted asbestos yarn comprising cotton and asbestos fibers, thedrafted asbestos fibers thereof being at least 85% of the whole, andsaid asbestos fibers being comparatively short and in major part capableof passing a screen of onehalf inch opening.

1'7. An asbestos yarn formed of a plurality of drafted-together andtwisted rovings, the asbestos fibres of which have an average staplelength not exceeding three-quarters of an inch. I

18. An asbestos yarn formed of a plurality of drafted-together andtwisted rovings, the asbestos fibres of which are capable in major partof passing a screen of one-half inch opening, said yarn being of anumerically greater size-cut than that of the original individualrovings.

BOUTWELL H. FOSTER.

